1. Field of the Invention
The present invention relates to detection of a reproduction signal, and more particularly, to a method of detecting only some of the outputs of an optical detection device, the detected outputs being least distorted or degraded, in an optical recording/reproduction system, and a circuit thereof.
2. Description of the Related Art
In the recording/reproduction system of optical recording media such as compact discs (CDs) and digital versatile discs (DVDs), data is manifested on a disc in the form of pits on a substrate or modifications of a recording film. Data on a disc is detected by illuminating the disc with a laser, and detecting light reflected back. In the recording/reproduction system, a signal is degraded due to a time delay between the outputs of an optical detection device. This time delay may be caused by the geometry (for example, the width, the length, the depth and the angle) of a data pit and a recording domain. This time delay may also be caused by interference between data in a tangential direction. When a time delay is caused between the outputs of an optical detection device, a reproduction signal is distorted. When the amplitude of the reproduction signal is not properly detected, the performance of the system is degraded.
Optical discs are being developed for high-density recording and high-speed reproduction, to record and/or reproduce a high definition (HD) image. As recording/reproduction systems are developed for high-density and high-speed recording/reproduction, inter-symbol interference increases, causing time delays between adjacent data and distortion and deterioration of the signal. Accordingly, the performance of the reproduction signal is degraded, requiring considerable effort and extra cost during implementation of the system.
The prior art apparatus for reproduction signal detection is shown in FIG. 1. First, in order to detect information recorded on a disc 100, a pickup unit (P/U) 102 radiates a beam emitted from a light source (for example, a laser diode) to the disc 100, and a multi-section optical detection device 104 (which can also be called a detection sensor) receives and divides an optical signal reflected by the disc 100 into multiple signals. The optical optical detection device 104 is conventionally a photodetector (PD).
First, second, third and fourth current/voltage (IV) converters 106, 108, 110 and 112 convert current signals A, B, C and D output by the optical detection device 104 into voltage signals. An arithmetic unit 114 sums the voltage signals output by the first, second, third and fourth IV converters 106, 108, 110 and 112, and outputs the sum as a radio frequency reproducing signal RF SUM.
In the prior art, a method of detecting a reproducing signal by simple addition of the outputs of the I/V converters 106, 108, 110 and 112 is adopted. Disadvantages of this method are that the reproducing signal is degraded due to the data conditions recorded on the disc, crosstalk, interference between optical signals reflected/diffracted from pits in close proximity to each other, from adjacent tracks on a recording medium, and from other problems with a system (for example, defocusing, detracking and tilting). Therefore, the quality of the reproducing signal and the performance of the system are degraded.